where \(F(u)\)  is some given but otherwise arbitrary function of a single variable \(u\)  (to be chosen so that restrictions of classical causality and quantum
unitarity be met as well[1]}, [2]}). Clearly unless there is no dependency on \({\cal P}\)  at all — which
would lead back to MLE — any such Lagrangian density is nonanalytic at \(({\cal S},{\cal P})=(0,0)\) . In such instance the fate of the null solutions
of MLE, in particular of null knots inclusive of the HR one, remains an open question for whatever conformally invariant NLE theory.
